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Proterozoic |
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Proterozoic [¦präd·ə·rə¦zō·ik] (geology) Geologic time between the Archean and Paleozoic eras, that is, from 2500 million to 550 million years ago. Also known as Algonkian. How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content. |
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| The quartz veins in the B and C Zones are related to major fault zones of the Upper Proterozoic Age that cross-cut older metamorphic volcano-sedimentary rocks of the Guarayos Greenstone Belt. Those of Paleozoic and Proterozoic age are usually more deeply eroded, and consist of flood basalt remnants and a deep-level plumbing system (of giant dyke swarms, sill provinces and layered intrusions). Paleoproterozoic orogens involved the assembly of pre-existing crustal fragments and microcontinents of both Archean and older Proterozoic age, and thus the shape and strength of the collided elements played a key role in orogenic style and evolution. |
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